Immune Surveillance in the Peyer’s Patches of Mice Following Acute High-Intensity Exercise

Purpose: The immune surveillance theory in exercise immunology suggests that exercise redistributes immune cells to peripheral organs, including the gut. High-intensity exercise temporarily increases intestinal permeability, allowing the translocation of gut bacteria. This study investigated changes in phagocytes, T cells, and Th17 cell responses in Peyer’s patches (PPs), where access to gut bacteria is facilitated after acute intensive exercise in mice. Methods: Mice underwent exhaustive swimming. Serum was obtained 1 h post-exercise. PP was collected 0, 1, and 4 h post-exercise. Results: The exercise group exhibited elevated serum lipopolysaccharide levels compared to controls, indicating increased gut permeability. Alterations in immune cell composition and activation markers in PP were evident at 1 h but not immediately (0 h) post-exercise. The proportions of dendritic cells (CD11c+) and macrophages (F4/80+) increased by 62% and 46%, respectively, while T (CD3+) and B cell (CD19+) proportions remained. Activation marker analysis revealed 48% and 25% higher frequencies of CD86-expressing cells among the CD11c+ cells and CD69-expressing cells among the T cells. Enhanced phagocytosis in PP cells was attributed to higher phagocyte proportions, not increased phagocytic capacity. Th17 cells increased by 72%, accompanied by upregulation of Th17-related genes, including IL-17F, IL-22, IL-23, CCL20, G-CSF, IFN-γ, and the immunoregulatory IL-10. T regulatory cell proportions and early inflammatory gene expression, including TNF- and IL-6, showed no significant changes. Conclusions: Acute exercise activates phagocytes and T cells, triggering Th17 cell response in the PP. These results provide further evidence for the immune surveillance theory, highlighting the role of PPs as a critical site for exercise-induced immune response.